HOW THE LITTLE ‘LIZARDS’ DISAPPEARED

NOT all the amphibians were large, for many very interesting kinds, of Carboniferous and Permian age, have been grouped under the name of Microsauria, or ‘little lizards.’ The name is not altogether misleading, because they were certainly small, and in some characters were intermediate between the reptiles and the amphibians. Their remains were first discovered in fossilised tree trunks in Nova Scotia, and apparently in Coal Measure times the little animals had been trapped there accidentally. Numerous other examples have been obtained from Bohemia, Ireland and England.

Despite the great number and variety of all these preceding kinds, they did not survive the Trias, but gave way in the struggle with the more highly-equipped reptiles. Fossil examples of the ancestors of living amphibians, frogs, toads, newts and salamanders, are, however, known although they do not date back later than the Jurassic period.1 In the Eocene and Oligocene ages they are especially well known, and many beautifully preserved specimens have been found which show them to have been very closely similar to the living forms.

One salamander of especial interest must be mentioned. It is a form closely allied to a salamander now living in Japan, and one specimen, now in a Dutch museum, was described in 1726 under the name of Homo diluvii testis, ‘man a witness of the deluge,’ as the physician who originally identified it believed it to be the remains of a man who had perished in the Flood.

The amphibians now living have only a fraction of the importance of the group as it was in the early days, and the disappearance of the more varied and the larger forms must be attributed to the rise of the higher forms, to which the amphibia themselves gave birth, known as the reptiles. The transition from some amphibian (probably related to the Permian Labyrint’hodont Seymouria) to reptile was apparently accomplished in Carboniferous times, as a result of the genial conditions and abundant food supply, perhaps reacting favourably on one of the more successful land-living forms. At any rate in the Carboniferous period we have the first remains of this new class of animals, and by the Permian age they are widespread and greatly diversified.

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